Weight and Balance

The correct weight and balance of an aircraft is critical for

its safe operation.

Any changes that may adversly affect this safe operation ie

the addition of a larger battery must be approved by a GFA

qualified person.

The following program written in Microsoft Excel 2003 will

allow the calculation of weight and balance requirements in

accordance with the,[download] BASIC SAILPLANE ENGINEERING

manual.

The program which has evolved over the past 7 years follows as

closely as possible the GFA weight and balance forms,

[download ] W1 and W2.

No fancy computer skills are required other than the ability

to use the keyboard and mouse.

If you are using Excel 2007 only use the compatibility mode as

the huge increase in the available number of cells can cause

problems.

The program consists of several parts which we will explain as

we go.

The first is the W1 sheet, the areas in BLUE are for user

povided information and as can be seen looks very much like

the standard GFA W1 form.

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After the aircraft is weighed in accordance with the manual

the various measurements are keyed into their respective areas

(BLUE).

As soon as all the information is keyed in the results of

these measurements will be shown in ORANGE areas.

It should be noted the program will only allow information to

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be entered in the BLUE areas.

The program has a data base which contains information on a

number of aircraft from their Type Data Sheets, this data base

can be user updated when required.

One feature that this data base has allowed is a drop down

menu in the location where you would normally insert the type

of aircraft.

A click of the mouse in area as shown above will will bring up

a list of aircraft in the data base; select the aircraft type

you want, an ASK21 Mi in this case as an example.

Selecting the aircraft that you require has two functions

first it leaves the name in the box, second is that all the

information in the data base for the selected aircraft is

transferred to the calculation sheet.

An explanation for the quick calulator seen to the right of

the main W1 sheet after it has been downloaded.

If the scales used to weigh the aircraft do not have the

required accuracy (100grams)to weigh the tailwheel, a separate

set of scales must be used. This calculator allows to input

the total weight (G) of the aircraft and when the tail wheel

weight is entered int the W1 sheet the calculation of the main

wheel weight (G1)is done automatically and transferred into

the W1 sheet.

The CALCULATION sheet takes this information as well as the

results from the W1 sheet to perform most of the calculations

for the weight and balance of the aircraft.

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This sheet has no user inputs all the information is gathered

from the W1 sheet and the data base. It shows a number of

basic calculations such as the minimum pilot weight,the empty

c/g, the safe c/g plus some information if it is a two

seat aircraft. It also shows what equations where used top get

these results,see manual.

This information is the automatically transferred to the

PLACARD sheet.

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This sheet then shows such information as minimum and maximum

pilot weights,maximum fuselage load, if applicable the effect

of carrying water as well as fixed items as required by the

manufacturer.

From this sheet the information can be transferred to suitable

material for the placards.

W2 sheet

This sheet allows number of user entry's which can be used to

verify that a modification to the aircraft ie that extra

battery does not cause the aircraft to move outside the

allowable limits for both c/g position or weight limits

All the calculations are done automatically and will be

displayed Red if they are outside the limits or Green if all

is ok.

To save all the information click of File, Save As and change

the name of the file,it can be your choice but is best if you

use the aircraft registration letters.

The program does not cover all possibilities and attention

should be paid to the manufacturer's requirements. Some

aircraft like the DG 1000 which can have up to 12Kg of

removable ballast in the tailfin require special attention, in

some powered sailplanes the location of the fuel tank can have

a great effect on the c/g as well as the all up weight.

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This program makes doing the calculations very easy but it

does not take away the duty of care of the user to ensure that

all the information is correct.

There are a couple of other features to the program which may

be of interest and of some use, if you are interested I can

give you the details.

The program is presented as is and is totally for you to use

as you wish, I make no promise that it is 100% accurate that

is where your duty of care comes in, I only ask that if you do

make any modifications that you think are worthwile that you

let me know.

As noted earlier program was written useing Microsoft Excel

2003, I have used Excel 2007 without any problems just use the

save as 97-2003 option and click "continue" when it comes up

with the compatability screen.

Cliff Wylie, lwyl5744@internode.on.net, I will answer all

mails.

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